This invention pertains to fuel injection systems for internal combustion engines, and in particular to ways for increasing the amount of fuel delivered during warm-up.
In many fuel injection pumps, the stroke of the pump is varied according to the amount of air, or the air pressure, within the intake manifold.
Often a tube will connect from the intake manifold to a sensing cylinder means which controls the stroke of the pump. In a variable-leverage fuel injection pump, the sensing cylinder means is connected to a power fulcrum, which it extends or retracts, according to changes in pressure within the intake manifold.
The power fulcrum, in turn, varies the lengths of lever arms within the fuel injection pump transmission, varying the stroke of a pump element. The stroke of the pump increases with an increase in pressure within the intake manifold, and decreases with a decrease in the pressure within it.
When an engine is started from cold, and until it warms itself, additional fuel must be supplied, or the engine will run poorly or quit entirely.
A convenient way to supply such a rich mixture is by temporarily opening the sensing cylinder to the outside air (which is called bleeding it), to abnormally raise the pressure inside the sensing cylinder, increasing the stroke of the pump element, and causing the engine to receive as much fuel as it would with an open throttle.
To accomplish this, a bleed tube is extended from the sensing cylinder to within the operator's reach, and is connected to a valve which is opened to enrich the mixture.
In a few minutes, after the engine has warmed itself, the enrichment bleed is closed and the engine operates normally.
If the enrichment bleed means is left open after the engine has warmed, it will run poorly, and fuel will be wasted.
Parenthetically, the question may be asked as to why the enrichment bleed should not be automatically controlled by a thermostatically controlled valve. The answer is that all automatic devices are subject to partial or complete failure, usually without giving an indication of such failure to the operator. They may function correctly when they leave the factory, but sooner or later-- maybe ten years later-- they'll quit working, with bad results. A manual enrichment bleed is too simple to fail.
In the coming years, with ever-increasing fuel scarcity and cost, drivers will want to operate their engines as economically as possible, which will be an important factor in the success of a manual enrichment bleed system.
The problem is to provide some sure means of keeping the open enrichment bleed on the operator's mind until he closes it.